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MESSENGER


MESSENGER's next big event will be its third flyby of Mercury, planned for September 29.
Mercury is the least explored terrestrial planet; fully half of the little rocky world has never been seen up close. MESSENGER will change that, capturing a comprehensive survey of the planet's cratered and rocky surface, vaporous atmosphere, and inexplicable magnetic field using seven science instruments. "MESSENGER" is an acronym that stands for MErcury Surface, Space ENvironment, GEochemistry, and Ranging. Once it reaches Mercury, the mission will last 1 Earth year, which corresponds to 4 Mercury years, but only 2 Mercury solar days!

MESSENGER is now in transit to Mercury, but the journey will take a very long time. To conserve on fuel, the spacecraft must rely on gravity assist flybys of Earth, Venus (twice), and Mercury (3 times) before settling into orbit around Mercury in March of 2011. The Earth flyby took place successfully on August 2, 2005, and the two Venus flybys on October 24, 2006 and June 5, 2007. It has also completed two of three Mercury flybys, the first on January 14, 2008, and the second on October 6, 2008. It will have one more flyby, on September 29, 2009, before settling into orbit on March 18, 2011. The first two flybys returned the first images sent from Mercury in 33 years, and have covered the majority of the 60% of the planet not previously seen by spacecraft.

MESSENGER Facts
Launch date: August 3, 2004 at 06:15:56 UTC
Mercury flybys: January 14 and October 6, 2008 and September 29, 2009
Mercury orbit insertion: planned for March 18, 2011
Primary mission end: March 2012